Compliant slip assembly for securing well tools in a tubing string

ABSTRACT

A compliant slip assembly that can include a spacer ring, a wedge ring, and a compliant slip device, where the slip device can include a body with a rigid first portion, a compliant second portion, and an expandable third portion, where the third portion can include expandable segments that are circumferentially spaced apart with a slit located between adjacent expandable segments. A method of securing a well tool in a tubing string using the compliant slip assembly, where the method can include conveying the well tool into a tubing string and expanding the compliant slip assembly into engagement with the tubing string, thereby securing the well tool in the tubing string.

TECHNICAL FIELD

A compliant slip assembly and methods of securing well tools in a tubing string using the compliant slip assembly are provided. The compliant slip assembly can include a compliant slip device with a body that can have a rigid first portion, a compliant second portion, and an expandable third portion, where expanding the third portion secures the well tool in the tubing string. According to certain embodiments, the compliant slip assembly is used in an oil or gas well operation.

BRIEF DESCRIPTION OF THE FIGURES

The features and advantages of certain embodiments will be more readily appreciated when considered in conjunction with the accompanying figures. The figures are not to be construed as limiting any of the preferred embodiments.

FIG. 1 depicts a cross-sectional view of a wellbore containing a frac plug that includes multiple compliant slip assemblies for securing the frac plug in the wellbore.

FIG. 2 depicts a cross-sectional view of the frac plug of FIG. 1 without the wellbore and surrounding earth formation being shown.

FIGS. 3A-C depict multiple views of a compliant slip device according to certain embodiments that can be utilized in the compliant slip assemblies in FIGS. 1 and 2.

FIGS. 3D-F depict detailed views of configurations of a slit in FIG. 3C.

FIGS. 4A-C depict multiple views of a compliant slip assembly according to certain embodiments in an unexpanded configuration.

FIGS. 5A-C depict multiple views of a compliant slip assembly according to certain embodiments in an expanded configuration.

FIGS. 6A-B depict multiple views of a compliant slip assembly according to certain other embodiments in an unexpanded configuration.

FIGS. 7A-B depict multiple views of a compliant slip assembly according to certain other embodiments in an unexpanded configuration.

DETAILED DESCRIPTION

Oil and gas hydrocarbons are naturally occurring in some subterranean formations. In the oil and gas industry, a subterranean formation containing oil or gas is referred to as a reservoir. A reservoir may be located under land or off shore. Reservoirs are typically located in the range of a few hundred feet (shallow reservoirs) to tens of thousands of feet (ultra-deep reservoirs). In order to produce oil or gas, a wellbore is drilled into a reservoir or adjacent to a reservoir. The oil, gas, or water produced from a reservoir is called a reservoir fluid. As used herein, a “fluid” is a substance having a continuous phase that tends to flow and to conform to the outline of its container when the substance is tested at a temperature of 71° F. (22° C.) and a pressure of one atmosphere (atm) (0.1 megapascals (MPa)). A fluid can be a liquid or gas.

A well can include, without limitation, an injection well, or an oil, gas, or water production well. As used herein, a “well” includes at least one wellbore. A wellbore can include vertical, inclined, and horizontal portions, and it can be straight, curved, or branched. As used herein, the term “wellbore” includes any cased, and any encased, open-hole portion of the wellbore. The well can also include multiple wellbores, such as a main wellbore and lateral wellbores. As used herein, the term “wellbore” also includes a main wellbore as well as lateral wellbores that branch off from the main wellbore or from other lateral wellbores. A near-wellbore region is the subterranean material and rock of the subterranean formation surrounding the wellbore. As used herein, a “well” also includes the near-wellbore region. The near-wellbore region is generally considered to be the region within approximately 100 feet radially of the wellbore. As used herein, “into a well” means and includes into any portion of the well, including into the wellbore or into the near-wellbore region via the wellbore.

In an open-hole wellbore portion, a tubing string may be placed into the wellbore. The tubing string allows fluids to be introduced into or flowed from a remote portion of the wellbore. In a cased-hole wellbore portion, a casing is placed into the wellbore that can also contain a tubing string. A wellbore can contain an annulus. Examples of an annulus include, but are not limited to, the space between the wellbore and the outside of a tubing string in an open-hole wellbore; the space between the wellbore and the outside of a casing in a cased-hole wellbore; and the space between the inside of a casing and the outside of a tubing string in a cased-hole wellbore.

It is not uncommon for a wellbore to extend several hundred feet or several thousand feet into a subterranean formation. The subterranean formation can have different zones. A zone is an interval of rock differentiated from surrounding rocks on the basis of its fossil content or other features, such as faults or fractures. For example, one zone can have a higher permeability compared to another zone. Each zone of the formation can be isolated within the wellbore via the use of packers, frac plugs, or other similar devices. At least one wellbore interval corresponds to each zone.

It is often desirable to produce a reservoir fluid from multiple zones of a formation. However, there are problems associated with fracturing or injecting into multiple formation zones. Fracturing a second zone after a first zone has been fractured can cause significant fluid loss through the fractures in the first zone. This fluid loss can possibly prevent a fracturing fluid from being delivered to the second zone at a pressure above a fracture pressure of the second zone, thereby preventing fractures from forming in the second zone. Therefore, it may be desirable to pressure isolate the first zone from the second zone by installing a packer, frac plug, etc. in a flow passage of a tubing string (e.g., casing string) to divert the fracturing fluid from the first zone to the second zone, thereby fracturing the second zone. It should be understood that, as used herein, “first,” “second,” “third,” etc., are arbitrarily assigned and are merely intended to differentiate between two or more materials, isolation devices, wellbore intervals, etc., as the case may be, and does not indicate any particular orientation or sequence. Furthermore, it is to be understood that the use of the term “first” does not require that there be any “second,” and the use of the term “second” does not require that there be any “third,” etc.

A bridge plug is composed primarily of slips, a plug mandrel, and a rubber sealing element. A bridge plug can be introduced into a wellbore and the sealing element can be caused to block fluid flow into downstream intervals. A packer generally consists of a sealing device, a holding or setting device, and an internal flow passage for fluids. A packer can be used to block fluid flow through the annulus located between the outside of a tubular and the wall of the wellbore or inside of a casing. A frac plug generally consists of slips, a plug mandrel, a rubber seal element, and an internal flow passage for fluids. During fracturing and/or injection operations, the frac plug can be introduced into a wellbore to block fluid flow into downstream elements, similar to a bridge plug. However, in addition to the rubber seal element that seals an annulus between the plug mandrel and the tubing string, the frac plug has an internal flow passage that must be blocked to prevent fluid flow to downstream intervals. An object can be dropped or circulated to a seal seat, thereby blocking fluid flow through the internal flow passage. When the injection operation is complete, production fluid can flow up through the frac plug, thereby circulating the object back to the surface.

Isolation devices (such as bridge plugs, packers, frac plugs, etc.) can be classified as permanent or retrievable. While permanent isolation devices are generally designed to remain in the wellbore after use, retrievable devices are capable of being removed after use. It is often desirable to use a retrievable isolation device in order to restore fluid communication between one or more wellbore intervals. Traditionally, isolation devices are retrieved by inserting a retrieval tool into the wellbore, wherein the retrieval tool engages with the isolation device, attaches to the isolation device, and the isolation device is then removed from the wellbore. Another way to remove an isolation device from the wellbore is to mill at least a portion of the device or the entire device. Yet, another way to remove an isolation device is to contact the device with a solvent, such as an acid, thus dissolving all or a portion of the device.

The slips in these isolation devices can be a slip ring assembly with multiple slip segments for securing an isolation device in a tubing string. During introduction of the isolation device into the tubing string, it is desirable to prevent detachment of the slip segments until the isolation device is positioned at a desired location in the tubing string. One example used to prevent detachment of these segments is a slip ring assembly that can include individual slip segments assembled in a ring around a mandrel and held in place by one or more bands. The inclusion of the bands requires additional manufacturing steps, thereby increasing the cost of the slip assembly. Once positioned in the wellbore, a wedge ring can be used to expand the slip segments into gripping engagement with an inside wall of the tubing string. The wedge ring can be forced underneath the ring of segments, thereby producing sufficient radial force to fracture the bands. The fractured bands release the slip segments and allow radial expansion of the slip segments into contact with the tubing string. However, the fractured bands can become trapped between the segments and tubing string, thereby undermining their gripping engagement with the tubing string and reducing a gripping force of the slip assembly. The fractured bands can also become trapped between an expandable seal element and the tubing string, thereby possibly causing leakage around the device.

Another example for retaining slip segments on a mandrel is to make the slip segments as a single piece ring with longitudinal fracture sites between each potential slip segment. Each fracture site can be a longitudinal recess cut into an outer and/or inner surface of the slip device assembly or the fracture site can be a thin interface between the slip segments. When sufficient radial expansion force is produced by the wedge ring, the fracture sites can fracture, resulting in multiple individual slip segments that can then be expanded into gripping engagement with the tubing string. However, this example can also cause problems. When one or more of the fracture sites are fractured, less force can be applied to the remaining fracture sites due to the separation of some slip segments from the single piece ring. This non-uniform fracturing of the fracture sites can result in misalignment of the slip segments during radial expansion and can undermine the gripping engagement of the slip segments with the tubing string. Therefore, there is a need to provide a slip device assembly that does not require bands to secure the slip segments and provides for consistent alignment during radial expansion.

It has been discovered that a single-body compliant slip device can reduce or eliminate the problems of the slip device assembly examples given above. As used herein, “compliant” refers to a material that can undergo deformation (e.g., elastic, plastic, etc.) when subjected to an applied force, and the deformation is performed without fracturing. For example, a thin piece of metal (or any other suitable material) connected between two rigid objects may bend or fold when one of the objects moves relative to the other object, but the thin metal does not lose connection between the objects during the deformation. However, the thin metal can also be designed to fracture after it undergoes a predetermined amount of deformation, and the thin metal can still be referred to as being “compliant.”

According to certain embodiments, a compliant slip assembly is provided for securing tools in a tubing string, where the compliant slip assembly can include a wedge ring and a compliant slip device. The compliant slip device can include a body with a substantially constant outer diameter from a first end to a second end when the slip device is unexpanded, and the body can include first, second, and third portions, where the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit between adjacent expandable segments.

According to other embodiments, a method of securing a well tool in a tubing string is provided, where the method can include conveying the well tool with a compliant slip assembly to a predetermined location in the tubing string, where the compliant slip assembly can include a wedge ring and a compliant slip device. The compliant slip device can include a body with a substantially constant outer diameter from a first end to a second end when the slip device is unexpanded, and the body can include first, second, and third portions, where the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit between adjacent expandable segments. The method can also include expanding the compliant slip assembly into engagement with the tubing string, thereby securing the well tool in the tubing string.

According to yet other embodiments, a compliant slip device can include a body with a substantially constant outer diameter from a first end to a second end when the compliant slip device is in an unexpanded configuration, and first, second, and third portions of the body, where the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit between adjacent ones of the expandable segments. The body can be a single piece with the first, second, and third body portions integral to the body, with the second body portion formed between the first and third body portions, and the second body portion being deformed to allow the third body portion to radially expand while the first body portion is prevented from expanding. As used herein, a “single-piece” body can include 1) a body that is made from a single block of material, 2) a body that is made from a mold that forms a single body, 3) a body that is formed from bonding multiple pieces together to form the body, where each piece can include one or more expandable segments, and 4) a body that is made by fastening individual pieces together to form the body, where each piece can include one or more expandable segments, etc.—so long as the final product yields a single body that can be installed in an assembly as one piece. For example, the single body can be slipped onto a mandrel as a single piece when assembling a compliant slip assembly 32, 36 (see FIGS. 1, 2). Gripping devices, such as buttons, wickers, etc. can be fixed to the body, however the body is still considered to be a single-piece body.

According to yet other embodiments, a compliant slip device can include a body with a substantially constant outer diameter from a first end to a second end when the compliant slip device is in an unexpanded configuration, and first, second, and third portions of the body, where the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit between adjacent ones of the expandable segments. The compliant slip device can be introduced into the wellbore without a retainer (e.g., one or more bands, molded ring, etc.) being positioned external to the compliant slip device, where the “retainer” is used herein to mean a device or structure that is used to prevent radial expansion of the expandable segments during the introduction and/or positioning of the compliant slip device at a predetermined location in the wellbore. Alternatively, or in addition to, the expandable segments can be expanded downhole without fracturing and/or breaking a material or structure that would prevent expansion of the segments prior to the fracturing or breaking of the material or structure.

According to vet other embodiments, a compliant slip assembly is provided for securing tools within a tubing string, where the compliant slip assembly can include a wedge ring and a compliant slip device. The compliant slip device can include a body with a substantially constant outer diameter from a first end to a second end when the slip device is unexpanded, and the body can include first, second, and third portions, where the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit between adjacent expandable segments. Engagement of the expandable segments with a tubing string causes the second portion to fracture, which disconnects the expandable third body portion from the rigid first body portion after the second body portion undergoes a predetermined deformation.

According to yet other embodiments, a compliant slip assembly is provided for securing tools within a tubing string, where the compliant slip assembly can include a retainer sleeve, a wedge ring, and a compliant slip device. The compliant slip device can include a body with first, second, and third portions, where the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit between adjacent expandable segments. The retainer sleeve encircles the expandable segments and prevents radial expansion of the segments during introduction into the tubing string. When the slip assembly is positioned at a predetermined location in the tubing string, a compressive force is applied to the wedge ring and compliant slip device, thereby fracturing the retainer sleeve and allowing radial expansion of the expandable segments into a gripping engagement with the tubing string.

According to vet other embodiments, a compliant slip assembly is provided for securing tools within a tubing string, where the compliant slip assembly can include a wedge ring and a compliant slip device. The compliant slip device can include a body with first, second, and third portions, where the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit between adjacent expandable segments. The compliant slip device can include multiple individual expandable segments that can be assembled to a spacer ring by an attachment means to form the body. As used herein, “attachment means” refers to items that are attached by bonding (such as welding, gluing, heat forming, fusion, etc.) and/or fastening (such as with screws, bolts, rivets, etc.). The “attachment means” can also refer to retaining the individual segments to the spacer ring by surrounding the segments with a layer of material (e.g., one or more bands, one or more sleeves, etc.). Any discussion of the embodiments regarding the compliant slip assembly or any component related to the compliant slip assembly is intended to apply to all of the apparatus and method embodiments.

Turning to the Figures, FIG. 1 depicts a wellbore 10 that has been drilled through an earth formation 20. A tubing string 14 (e.g., a casing string) has been installed in the wellbore 10 and cement 12 has filled an annulus between the wellbore and the tubing string 14, and this wellbore configuration is generally referred to as a cased wellbore. However, it is not a requirement for the wellbore to be cased. The tubing string can be installed in an uncased well without the annulus being filled with cement. The tubing string can also be installed in another tubing string in the wellbore. Therefore, it should be clearly understood that the compliant slip assembly can be used in many wellbore configurations.

Referring again to FIG. 1, the first wellbore interval 16 can be associated with a lower formation zone, and the second wellbore interval 18 can be associated with an upper formation zone. It can be desirable to perform separate fracturing and/or treatment operations in the wellbore intervals 16, 18 for the lower and upper zones. Conventionally, the casing of the first wellbore interval 16 is perforated first, and then these perforations are fractured by pumping fracturing fluid into the perforations at a pressure higher than a fracture pressure of the lower zone. To fracture the upper zone, perforations are made in the casing of the second wellbore interval 18. It may be desirable to isolate different subterranean formation zones by isolating the first wellbore interval 16 from the second wellbore interval 18 by setting an isolation device (such as a frac plug 30, bridge plug, packer, etc.) in the tubing string 14 at a location between the first wellbore interval 16 and the second wellbore interval 18. The frac plug 30 (or isolation device) can be run into the tubing string 14 on a conveyance to a desired location in the tubing string 14. As used herein, “conveyance” refers to a means of transporting the frac plug 30 (or isolation device) through the tubing string 14, such as coiled tubing, a wireline, a tractor system, a segmented tubing string, etc. A setting tool (not shown) connected to the conveyance can be used to set the frac plug 30 at the desired or predetermined location. Once the frac plug 30 is set, an object can be dropped to land in a seal seat at an upper end of the frac plug 30, thereby blocking fluid flow through the frac plug 30 and pressure isolating the first wellbore interval 16 from the second wellbore interval 18. The upper zone can then be fractured by pumping the fracturing fluid into the perforations in the second wellbore interval 18 at a pressure higher than a fracture pressure of the upper zone.

The frac plug 30 can include an upper compliant slip assembly 32, a seal assembly 34, and a lower compliant slip assembly 36. FIG. 1 depicts the compliant slip assemblies 32, 36 in their initial run-in configuration, where the outer diameter D4 of the compliant slip assemblies is less that the outer diameter D2, which is the maximum outer diameter of the frac plug 30 in the initial (or unexpanded) configuration. The diameter D2 is less than the inner diameter D1 of the tubing string 14 to facilitate movement of the frac plug 30 through a flow passage 28 of the tubing string 14 to the predetermined location. An upper end 38 of the frac plug 30 can be connected to a setting tool (not shown) and conveyed into the tubing string 14 on the setting tool via a conveyance.

When the frac plug 30 is at the predetermined location, the setting tool can be used to set the frac plug 30 by pulling up on the mandrel 26 of the frac plug 30 while forcing the compliant slip assembly 32 down, thereby compressing the slip and seal assemblies 32, 34, 36 and radially expanding these assemblies into engagement with the tubing string 14. When the assemblies 32, 34, 36 are expanded, the outer diameter D6 of the seal assembly 34 and the outer diameter D4 of the compliant slip assemblies 32, 36 are increased by radial expansion until they are generally equal to the inner diameter D1 of the tubing string 14. The engagement of these assemblies 32, 34, 36 with the tubing string 14 provides a gripping force that prevents further longitudinal movement of the frac plug 30 and seals off an annulus between the frac plug mandrel 26 and the tubing string 14. Therefore, when an object (e.g., ball, dart or other blocking device) is dropped through the tubing string to the frac plug 30 and engages a seal at the end 38, the internal flow passage (with inner diameter D5) is sealed off and wellbore intervals 16, 18 are pressure isolated from each other.

Please note that the frac plug 30 shown in FIG. 1 is only one example of an isolation device that can benefit from the compliant slip assembly of this disclosure. For example, an isolation device such as a bridge plug may not include an internal flow passage. Therefore, dropping balls or darts would not be necessary to pressure isolate the wellbore intervals 16, 18 when the bridge plug is set. Additionally, a packer or other isolation device may benefit from utilizing the compliant slip assemblies 32, 36 of this disclosure.

FIG. 2 depicts the frac plug 30 without the surrounding wellbore 10, tubing string 14, or earth formation 20 for clarity. The end 38 of the frac plug can be used to connect to a setting tool (not shown) during run-in. As mentioned above, the frac plug 30 can include the compliant slip assemblies 32, 36 and the seal assembly 34. These assemblies 32, 34, 36 can be slideably mounted on a mandrel 26. The upper slip assembly 32 can include a spacer ring 50, a compliant slip device 40 and a wedge ring 60. The spacer ring 50 abuts a shoulder of the mandrel at end 38, which can have a radially enlarged diameter D3. The compliant slip device 40 can be slipped over an end of the spacer ring 50 such that the compliant slip device 40 overlaps a portion of the spacer ring 50. Inclined surfaces 62 on the wedge ring 60 partially engage respective inclined surfaces 44 of the compliant slip device 40. The spacer ring 50 and the wedge ring 60 are depicted as having a shear device 24 that prevents movement of these rings 50, 60 relative to the mandrel 26 during run-in of the frac plug 30. The lower slip assembly 36 is depicted as being very similar to the upper slip assembly 32, except that the spacer ring 50 is shown as a mule shoe 50. However, it should be clearly understood that the spacer ring 50 is not required. The slip device 40 can provide engagement interfaces for an application of a compressive force applied to the slip device 40 and the wedge ring 60 to force the wedge ring 60 underneath the expandable segments 90 of the compliant slip device 40.

The seal assembly 34 can include an expandable seal element 70 and end rings 72, 74. The wedge ring 60 of the upper slip assembly 32 can abut the end ring 72, and the wedge ring 60 of the lower slip assembly 36 can abut the end ring 74. Moving the upper and lower wedge rings 60 toward each other can result in compressing the seal element 70. The setting tool can apply a tensile force F1 to the mandrel 26 while applying a compressive force F2 to an engagement surface 52 of the spacer ring 50 of the upper slip assembly 32. The tensile force F1 urges the lower slip assembly 36 to move toward the upper slip assembly 32, thereby compressing the components of the assemblies 32, 34, 36 between the spacer ring 50 of the upper slip assembly 32 and the spacer ring 50 of the lower slip assembly 36. When the compression force acting on these components reaches a predetermined level, various shear devices 24 will shear allowing the components to slide along the mandrel 26. As the spacer ring 50 of the upper slip assembly 32 moves downward, a surface 56 of the spacer ring 50 abuts a surface 42 of the compliant slip device 40, thereby moving the compliant slip device 40 along inclined surfaces 62 of the wedge ring 60 and radially expanding the compliant slip device 40 into gripping engagement with the tubing string 14.

The shear device 24 in the upper wedge ring 60 will shear allowing the upper wedge ring 60 to slide on the mandrel 26 toward the lower wedge ring 60, thereby compressing the seal element 70 between the end rings 72, 74 and radially expanding the seal element 70 into engagement with the tubing string 14. Similarly, compression of the components of the lower slip assembly 36 will shear one or more shear devices 24 and move the compliant slip device 40 along inclined surfaces 62 of the lower wedge ring 60, thereby radially expanding the compliant slip device 40 into gripping engagement with the tubing string 14. The spacer ring (or mule shoe) 50 of the lower slip assembly 36 can be threaded onto the bottom end of the mandrel 26. Therefore, the tensile force F1 applied to the mandrel 26 is transmitted through the threaded connection to the spacer ring 50 of the lower slip assembly 36 and opposes the compressive force F2 applied to the upper spacer ring 50, thereby applying a compression force to the components of the assemblies 32, 34, 36. The shear device 24 in the spacer ring 50 of the lower slip assembly 36 can prevent premature unthreading of the spacer ring 50 from the lower end of the mandrel 26.

FIGS. 3A-C depict various views of the compliant slip device 40 in an unexpanded configuration. FIG. 3A depicts a perspective view, FIG. 3B depicts and end view, and FIG. 3C depicts a side view of the compliant slip device 40. The compliant slip device 40 can be a single body where all components of the ring 40 are integral to a body 41 (the gripping devices 22 can be fixedly attached to an outer surface 69 of the body 41 after the body 41 is formed). Prior to the compliant slip device 40 being expanded, the body 41 is generally a constant diameter D4 from a first end 46 to a second end 47 of the body 41. The compliant slip device 40 can include first, second, and third portions 82, 84, 86 of the body 41. The first body portion 82 can be a rigid region of the body of length L2 that does not expand when the compliant slip device 40 is radially expanded into gripping engagement with the tubing string 14. The third body portion 86 can include multiple expandable segments 90 with adjacent ones (or pairs) of the expandable segments 90, each being separated by a longitudinally extending slit 92. As used herein, “longitudinal” or “lonaitudinally” means generally parallel to a central axis 80 of the frac plug 30. The second body portion 84 can be a compliant region 98 disposed between the first body portion 82 and the third body portion 86. The compliant region 98 can allow the third body portion 86 to radially expand while allowing the first body portion 82 to remain rigid by deforming the second body portion 84. Please note that FIGS. 3A-C depict a compliant slip device 40 with eight expandable segments 90 and eight lonaitudinally extending slits 92. However, it should be clearly understood that any number of expandable segments 90 can be included in the compliant slip device 40.

The first body portion 82 includes an inner surface 48 and an outer surface 49. The second body portion 84 includes an inner surface 58 and an outer surface 59. The third body portion 86 includes an inner surface 68 and an outer surface 69. The outer surfaces 49, 59 and 69 can form a contiguous outer surface of the body 41 from the end 46 to the end 47, minus material that is removed when the slits 92 are formed and when recesses for receiving the gripping devices 22 are formed. The slits 92 can be longitudinally extending regions of the compliant slip device 40 that are void of material. The inner surfaces 48, 58 and 68 can form generally cylindrical surfaces with various inner diameters to facilitate operation with the spacer ring 50 and the wedge ring 60. The inner surfaces 48 and 58 can have generally the same diameter D8 when the compliant slip device 40 is in the unexpanded configuration. The diameter D9 of the inner surface 68 can be radially reduced from the inner diameter D8 of the inner surface 58, thereby forming a shoulder 42 on each of the expandable segments 90 at the transition between the inner surfaces 58, 68. The inner surface 68 can form an inclined surface 44 with a diameter that increases from the diameter D9 to a diameter D7 at the end 47 of the body 41 (diameter D7 and inclined surface 44 not shown, refer to FIG. 2). This inclined surface 44 can be used to radially expand the expandable segments 90 when the wedge ring 60 is forced into the end 47 of the body 41. It should be clearly understood that the inclined surface 44 can also be an annular arrangement of inclined planar surfaces, where a cross-sectional view of the inclined surface 44 can be the shape of a triangle, square, pentagon, hexagon, etc., depending on the number of inclined planar surfaces utilized.

Each slit 92 can extend longitudinally through the second body portion 84 and at least partially through the third body portion 86. Each slit 92 can be formed with a constant width W1 when the compliant slip device 40 is in the unexpanded configuration. These slits 92 allow the individual segments 90 to move independently when the compliant slip device 40 is being expanded. The slits 92 may not extend into the first body portion 82 because it is desirable that the first body portion 82 remain rigid and not expand during expansion of the second and third body portions 84, 86. However, these slits can also extend through the first body portion. A portion of each individual expandable segment can be fixedly attached by an attachment means to form a rigid first body portion. Each slit 92 includes an end 94 and an opposite end 96, where the end 96 is near the end 47 of the body 41, and the end 94 can be near a transition between the first and second body portions 82, 84. The length L1 is the combination of a length of the compliant region 98 and a length of the third body portion 86. The length L2 of the first body portion is the region that does not expand (i.e., is rigid). The overall length L3 of the body 41 is the sum of length L1 and length L2. These lengths L1, L2 can be adjusted as desired to change various characteristics of the compliant slip device 40, such as: increasing a radial expansion of the third body portion 86 by increasing the compliant region 98; or increasing the rigidity of the first body portion 82 by increasing the length L2, etc.

FIGS. 3D-F depict detailed views of the end 94 of a slit 92 in FIG. 3C. FIGS. 3D-F depict various embodiments of an end 96 of a single one of the slits 92. As seen in FIG. 3D, the slit 92 begins at the end 47 and continues to the end 94 (end 94 shown in FIG. 3C) without any material bridging across the slit 92 for the entire length L1 of the slit 92. This allows the expandable segments 90 to move independently of each other even during run-in of the frac plug 30. With this configuration, no fracturing of a bridging material is needed to allow expansion of the expandable segments 90 in the third body portion 86.

FIG. 3E depicts another configuration of the slit 92, where the slit 92 does not extend to the end 47 of the body 41 due to a tab 88 positioned at the end 47. The tab 88 can be formed by a material of length L4 that bridges between adjacent expandable segments 90. This tab 88 can be used to prevent expansion of the expandable segments 90 until the frac plug 30 is positioned in the tubing string 14 and the setting tool begins to expand the segments via the compression force. When the expandable segments 90 are expanded, the tab 88 is fractured, thereby allowing radial expansion of the segments 90. In this configuration, the length of the slit 92 is the length L1 minus the length L4 of the tab 88.

FIG. 3F depicts yet another configuration of the slit 92, where the tab 88 is positioned at a desired location along the slit 92, thereby dividing the slit 92 into two segments. One segment extends from the end 94 to the tab 88 and the other segment extends from the tab 88 to the end 47 of the body 41. The tab 88 can be formed by a material of length L4 that bridges between adjacent expandable segments 90. The length L4 is preferably less than 20% of the overall length L1 that includes the second and third body portions 84, 86. This tab 88 can be used to prevent expansion of the expandable segments 90 until the frac plug 30 is positioned in the tubing string 14 and the setting tool begins to expand the segments via the compression force. At this time, the tab 88 is fractured, thereby allowing radial expansion of the segments 90. In this configuration, the length of the slit would be length L1, which also includes the length L4 of the tab 88. Therefore, it should be clearly understood that it is not necessary that the slits 92 be void of material from the end 47 of the body 41 to the end 94 of each slit 92. It should also be clearly understood that each of these tabs 88 may include scores or notches along the inner and/or outer surfaces of the tab 88 to reduce the force needed to fracture these tabs 88 during radial expansion. Additionally, there may be multiple tabs 88 along each slit 92, thereby dividing each slit 92 into three or more segments.

FIGS. 4A-C depict the slip assembly 32 in the unexpanded configuration without the other assemblies 34, 36 or the mandrel 26 to more easily show the slip assembly. FIGS. 4A-B also depict the slip assembly 32 without the tubing string 14, which is shown in FIG. 4C. Please refer back to FIGS. 1-2 for the structural relationship between these omitted components and the slip assembly 32. FIGS. 4A-B depict the compliant slip device 40 positioned between the spacer ring 50 and the wedge ring 60. FIG. 4A is a perspective view and FIG. 4B is a side view of the slip assembly 32. In these figures, the wedge ring 60 is depicted as having multiple inclined planar surfaces 62 arranged in an annular ring that is generally shaped as a cone, but a cross-section of the wedge 60 at the inclined surfaces 62 would be octagon shaped, since there are eight planar surfaces on the wedge 60. These inclined surfaces 62 engage with inclined surfaces 44 on the compliant slip device 40 as shown in FIG. 4C. The compliant slip device 40 at least partially overlaps the wedge ring 60 when they are installed on the mandrel 26.

The spacer ring 50 is depicted in FIG. 4C as having a generally T-shaped cross section with an internal bore for positioning the ring 50 on the mandrel 26. The spacer ring 50 is inserted into an end 46 of the compliant slip device 40 until the engagement surface 56 of the ring 50 engages each of the shoulders 42 of the expandable segments 90, and the end 46 of the compliant slip device 40 engages (or is at least positioned near) the engagement surface 54 of the ring 50. However, it should be clearly understood that the spacer ring 50 is not required. The compliant slip device 40 can support force engagement and force distribution features of the spacer ring 50 without using a spacer ring 50. In the unexpanded configuration, the outer diameter D4 of compliant slip device 40 is substantially constant along the length of the slip device 40. As used herein, in reference to a diameter, “substantially constant,” “substantially equal,” or “substantially the same” means that the diameter does not vary by more than +/−10 millimeters when the slip device 40 is in the unexpanded configuration. Please note that the width W1 of each of the slits 92 is substantially constant along the length of each of the slits 92. As used herein, in reference to a width, “substantially constant” means that the width does not vary by more than +/−10 millimeters. As seen in FIGS. 4B-C, an outer diameter D4 of the unexpanded compliant slip device 40 is less than the inner diameter D1 of the tubing string 14, thereby allowing unrestricted movement of the slip assembly 32 in the tubing string 14.

FIGS. 5A-C depict the slip assembly 32 in an expanded configuration without the other assemblies 34, 36 or the mandrel 26. FIGS. 5A-B also depict the slip assembly 32 without the tubing string 14, which is shown in FIG. 5C. Please refer back to FIGS. 1-2 for the structural relationship between these omitted components and the slip assembly 32. FIGS. 5A-C depict the slip assembly 32 after the compression force has been applied to the assemblies 32, 34, 36 (see FIG. 2) via the setting tool. The compression force urges the spacer ring 50 and the wedge ring 60 toward each other and causes movement of the inclined surfaces 44 of the expandable segments 90 along the inclined surfaces 62 on the wedge ring 60. The engagement surface 56 of the spacer ring 50 engages the shoulders 42 on the expandable segments 90, forcing the expandable segments over the wedge ring 60, thereby expanding the segments 90 into engagement with the tubing string 14 and securing the slip assembly 32 to the tubing string. The engagement with the tubing string 14 can cause gripping devices 22 to engage the tubing string 14 by deforming a portion of the tubing string at an engagement site of each gripping device 22. Additionally, the compliant second body portion 84 can be designed to fracture only after a predetermined deformation of the compliant region 98 has occurred. As used herein, “predetermined deformation” means that the second body portion 84 deforms until the expandable third body portion 86 engages the inside of the tubing string 14. When this engagement occurs, the deformation of the second body portion 82 reaches an amount of deformation that causes the engagement segments 90 to fracture at some point along the length of the second body portion 82.

In the expanded configuration, the first body portion 82 maintains a diameter D4 (i.e., diameter remains unchanged), while the third body portion 86 extends to a diameter substantially equal to the inner diameter D1 of the tubing string 14. Stated another way, the first body portion 82 with diameter D4 does not substantially radially expand or contract while the third body portion 86 is being radially expanded. Stated yet another way, the first body portion 82 is substantially prevented from radially expanding or contracting during expansion of the third body portion 86 As used herein, the terms “remains unchanged,” “does not substantially radially expand or contract,” or “substantially prevented from radially expanding or contracting” means that the diameter of the first body portion is maintained within +/−10 percent of its initial diameter D4. It can be seen in FIGS. 5A-C that the second body portion 84 is deformed to maintain connection between the first and third body portions 82, 86. The second body portion 84 can form a generally frustum-conical shape with diameter D1 at one end and diameter D4 at the other end. Also, the outer surfaces 69 of the third body portion 86 are substantially parallel to the outer surface 49 of the first body portion 82 when the third body portion 86 is in the expanded configuration. In other words, the outer surfaces 69 of the third body portion 86 are coaxially aligned with the outer surface 49 of the first body portion 82. As used herein, “substantially parallel” means that the surfaces being compared are within +/−10 degrees of each other. In the expanded configuration, the portion of the slits 92 in the third body portion 86 have been increased from the width W1 shown in the unexpanded configuration (FIGS. 4A-C) to the width W2 shown in the expanded configuration (FIGS. 5A-C).

Referring back to FIG. 1, when the slip assemblies 32, 36 have been expanded into gripping engagement with the tubing string 14, the frac plug 30 is secured in the tubing string 14 at the predetermined location. The seal assembly has also been expanded into sealing contact with the tubing string 14, thereby preventing fluid flow past the frac plug through an annulus between the frac plug and the tubing string.

FIGS. 6A-B depict a compliant slip device 40 that is made up of individual expandable segments 90, where the slit 92 between each adjacent segment 90 extends through from the end 47 of the compliant slip device 40 to the other end 46. An end of each of the individual segments 90 can be inserted into a recess 57 in the annular surface 54 of the spacer ring 50. An attachment means can secure the ends of the segments 90 in the recess 57. The portion of the segments 90 secured in the recess 57 forms the rigid first body portion 82 of the compliant ring device 40. The compliant region 98 is depicted as being the region between the surface 54 and the shoulders 42 (see FIG. 5C) of the third body portion of the segments 90. In this certain embodiment, the spacer ring 50 and the compliant slip device 40 form a single body. The single body with spacer ring 50 and compliant device 40 combined will function similar to the compliant slip devices depicted in FIGS. 4A-5C. The expandable segments 90 can radially expand into engagement with an inside 15 of the tubing string 14 to secure the well tool 32 in the tubing string 14.

FIGS. 7A-B depict a compliant slip device 40 that is made up of individual expandable segments 90, where the slit 92 between each adjacent segment 90 extends through from the end 47 of the compliant slip device 40 to the other end 46. An end of each of the individual segments 90 can be secured to an annular surface 51 of the spacer ring 50 by an attachment means (e.g., fastener 45, threaded bolt and washer, screw, etc.). The portion of the segments 90 secured to the spacer ring 50 forms the rigid first body portion 82 of the compliant ring device 40. The compliant region 98 is depicted as being the region between the attachment means and the shoulders 42 (see FIG. 5C) of the third body portion of the segments 90. In this certain embodiment, the spacer ring 50 and the compliant slip device 40 form a single body. The single body with spacer ring 50 and compliant device 40 combined will function similar to the compliant slip devices depicted in FIGS. 4A-5C.

Therefore, the present system is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is, therefore, evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. As used herein, the words “comprise,” “have,” “include,” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods also can “consist essentially of” or “consist of” the various components and steps.

Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent(s) or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted. 

What is claimed is:
 1. A compliant slip assembly for securing tools in a tubing string comprising: a compliant slip device comprising: (A) a body with a substantially constant outer diameter from a first end to a second end when the slip device is in an unexpanded configuration; and (B) first, second, and third portions of the body, wherein the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit located between adjacent pairs of the expandable segments.
 2. The assembly according to claim 1, wherein the slits are present when the compliant slip device is in the unexpanded configuration.
 3. The assembly according to claim 2, wherein each of the slits radially extends between an inner surface and an outer surface of the third body portion.
 4. The assembly according to claim 1, wherein each of the slits extends longitudinally from the second end through the third and second portions of the body.
 5. The assembly according to claim 1, wherein a width of each of the slits increases as the third body portion is expanded.
 6. The assembly according to claim 1, wherein the compliant slip device is positioned on a mandrel between a spacer ring and a wedge ring, and wherein relative movement between the spacer ring and the wedge ring causes the expandable segments to radially expand into engagement with an inside of the tubing string.
 7. The assembly according to claim 6, wherein the movement causes an inclined surface on each of the expandable segments to engage with a respective inclined surface on the wedge ring, thereby radially extending the expandable segments.
 8. The assembly according to claim 1, wherein the compliant slip device is positioned on a mandrel with a wedge ring, and wherein relative movement between the compliant slip device and the wedge ring causes the expandable segments to radially expand into engagement with an inside of the tubing string.
 9. The assembly according to claim 1, wherein each slit extends longitudinally through the second portion of the body and at least partially through the third portion of the body, wherein a tab of material bridges across at least one of the slits, and wherein each tab secures adjacent expandable segments together and temporarily prevents expansion of the adjacent expandable segments.
 10. The assembly according to claim 9, wherein the compliant slip device is positioned on a mandrel between a spacer ring and a wedge ring, and wherein application of a predetermined compression force between the wedge ring and the spacer ring causes each of the tabs to break and allows the expandable segments to radially expand.
 11. The assembly according to claim 1, wherein an outer diameter of the first body portion remains unchanged when the compliant slip device is changed from an unexpanded configuration to an expanded configuration.
 12. The assembly according to claim 1, wherein the slip device is expanded into an expanded configuration, wherein an outer diameter of the second body portion increases along a length of the second body portion during expansion, and wherein the second body portion has a smallest outer diameter located adjacent to the first body portion and a largest outer diameter located adjacent to the third body portion when the slip device is in the expanded configuration.
 13. The assembly according to claim 1, wherein at least one gripping device is mounted to an outer surface of at least one of the expandable segments, wherein the at least one gripping device increases an amount of a gripping engagement between the expandable segments and the tubing string.
 14. The assembly according to claim 1, wherein an outer surface of the third body portion is coaxially aligned with an outer surface of the first body portion when the slip device is in an expanded configuration.
 15. The assembly according to claim 1, wherein an individual piece includes one or more of the expandable segments, and multiple of the individual pieces are assembled into the compliant slip device to form the body.
 16. The assembly according to claim 15, wherein a portion of each of the individual pieces is inserted into an annular recess formed in a spacer ring, wherein the portion of each of the individual pieces is retained by the annular recess and forms the rigid first portion of the body.
 17. The assembly according to claim 15, wherein a portion of each of the individual pieces is bonded or fastened to an annular surface of a spacer ring, wherein the portion of each of the pieces forms the rigid first portion of the body.
 18. A method of securing a well tool in a tubing string, the method comprising: conveying the well tool to a predetermined location in the tubing string, wherein the well tool includes a compliant slip assembly comprising: a compliant slip device comprising: (A) a body with a substantially constant outer diameter from a first end to a second end when the compliant slip device is in an unexpanded configuration; and (B) first, second, and third portions of the body, wherein the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit located between adjacent pairs of the segments; and expanding the compliant slip assembly into engagement with the tubing string, thereby securing the well tool at the predetermined location in the tubing string.
 19. The method according to claim 18, wherein the step of expanding further comprises applying a predetermined compression force between a spacer ring and a wedge ring, thereby moving the spacer ring toward the wedge ring and expanding the expandable segments in response to the movement.
 20. The method according to claim 18, wherein the compliant slip device is positioned on a mandrel between a spacer ring and a wedge ring, and wherein the step of expanding further comprises moving the spacer ring toward the wedge ring and causing an inclined surface on each of the expandable segments to engage with a respective inclined surface on the wedge ring, thereby radially extending the expandable segments.
 21. The method according to claim 18, wherein the step of expanding further comprises increasing a width of each of the slits from a first width to a second width when the compliant slip device is expanded.
 22. The method according to claim 18, wherein the first body portion is connected to the second body portion and the second body portion is connected to the third body portion, wherein the step of expanding further comprises radially expanding the third body portion, and wherein the rigid first body portion is substantially prevented from radially expanding during expansion of the third body portion.
 23. The method according to claim 22, wherein the step of expanding further comprises deforming the compliant second body portion into a generally frustum-conical shape, thereby allowing the second body portion to remain connected to the first and third body portions when the third body portion is radially expanded.
 24. The method according to claim 18, wherein at least one gripping device is mounted to an outer surface of at least one of the expandable segments, thereby increasing an amount of a gripping engagement between the expandable segments and an inside of the tubing string.
 25. The method according to claim 18, wherein an outer surface of the third body portion is coaxially aligned with an outer surface of the first body portion when the slip device is in an expanded configuration.
 26. A compliant slip device comprising: a body with a substantially constant outer diameter from a first end to a second end when the compliant slip device is in an unexpanded configuration; and first, second, and third portions of the body, wherein the first portion is rigid, the second portion is compliant, and the third portion includes multiple expandable segments that are circumferentially spaced apart with a slit located between adjacent pairs of the expandable segments, wherein the body is a single piece with the first, second, and third body portions integral to the body, wherein the second body portion is formed between the first and third body portions, and wherein the second body portion deforms to allow the third body portion to radially expand while the first body portion is substantially prevented from expanding.
 27. The device according to claim 26, wherein the expandable segments remain connected to the first body portion via the second body portion after the expansion of third body portion.
 28. The device according to claim 26, wherein engagement of the expandable segments with a tubing string causes the second body portion to fracture, which disconnects the expandable segments from the rigid first body portion. 